Process for growing silicon carbide whiskers by undercooling

Abstract

A method of growing silicon carbide whiskers, especially in the β form, using a heating schedule wherein the temperature of the atmosphere in the growth zone of a furnace is first heated to or beyond the growth temperature and then is cooled to or below the growth temperature to induce nucleation of whiskers at catalyst sites at a desired point in time which results in the selection.

What is claimed is: 
     
       1. A method of manufacturing β silicon carbide whiskers which comprises heating a reaction system consisting of a silicon source, a carbon source, and a catalyst in a reducing atmosphere whereby said reaction system is first heated beyond the whisker growth temperature and then said reaction system is cooled to a temperature to or below the growth temperature to induce nucleation at catalyst sites at a desired point in time, before being held at the growth temperature for the growth period. 
     
     
       2. The method of claim 1 wherein said growth temperature is from 1350° to 1500° C. 
     
     
       3. The method of claim 1 wherein said reducing atmosphere is a hydrogen atmosphere. 
     
     
       4. The method of claim 1 wherein said carbon source before whisker growth includes a graphite substrate. 
     
     
       5. The method of claim 1 wherein said silicon source is a SiO 2  and carbon powder mixture. 
     
     
       6. The method of claim 1 wherein said catalyst comprises one or more of the following metals: manganese, cobalt, nickel, iron, chromium, and silicon. 
     
     
       7. The method of claim 1 wherein said reaction system is cooled 150° C. below the growth temperature, before the growth period. 
     
     
       8. The method of claim 1 wherein said reaction system is heated up to 100° C. beyond the growth temperature before the growth period. 
     
     
       9. The method of claim 1 wherein said β silicon carbide whiskers are grown by the vapor-liquid-solid mechanism.